158 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



When the course of an artery is not straight, and when it is subjected 

 to bending of various grades, the circularly disposed fibres of its media 

 are reinforced by oblique or longitudinal bundles, the oblique fibres 

 occurring much more frequently than the longitudinal. These oblique 

 and longitudinal fibres are to be found in the middle coat in all periods 

 of life. It does not appear that these occur in any particular site of 

 development within the media. 



Spongiosa of Cetacean Pelvis.* — Willy Augustin took Rontgen 

 photographs of several specimens of rudimentary pelvic bones. They 

 showed the characteristic trajectories in the spongiosa. This is inter- 

 esting, since these rudimentary bones are connected only with muscles 

 (the tail-muscle, the genital muscles, and trunk muscles). 



Structure of Preen Gland. | — Hugo Granvik describes the structure 

 of the glandula uropy^ii in a number of types. He shows, for instance, 

 the presence of Herbst's corpuscles (modifications of Paccinian corpuscles) 

 in the fowl and some other birds, the secondary canals of the efferent 

 duct in the flamingo, the septum in Passer montanus, which is absent in 

 the house-sparrow, the very well-developed state of the gland in the 

 snow-bunting, and many other points. 



Structure of Preen Grland.J — P. Paris gives a detailed account of 

 the state of the preen gland in different orders of birds, and discusses 

 its vascularization, innervation, development, and use. He describes the 

 gland, which is present in most birds, and probably in all their embryos, 

 as a subcutaneous mass of variable but clearly-defined form, made up of 

 two equal lobes entirely or partly separate, but united at the apex in an 

 excretory nipple projecting on the integument, by which it is closely 

 invested. Each of the constituent lobes is autonomous — that is, each 

 has its own vascularization and innervation, and can secrete independently 

 of the other. Each lobe is surrounded by a capsule of connective-tissue 

 without smooth muscular fibres. It contains a great many glandular 

 tubules, separated from each other by thin partitions, of the same nature 

 as the enveloping capsule, which enclose the glandular epithelium. The 

 glandular tubes form a mass, sometimes single, sometimes sub-divided 

 into glandules within each lobe. The tubes are of varying length, and 

 they unite to form secondary ducts, which in their turn form the primary 

 ducts. These ducts may be wholly or partly absent, in which case the 

 secretion is collected in a cavity at the apex of each lobe and is discharged 

 to the exterior by an excretory canal through the nipple. Each lobe 

 has thus at least one excretory canal, except in a few cases {Gaprimulgus 

 europseus, Upupa epops), which have only a single duct for the whole 

 gland. The glandular epithelium is formed by several — at least three — 

 layers of secretory cells, which increase progressively in size from the 

 periphery to the axis of the tube. Primitively triangular, they become 

 polyhedral, then globular in form. These secretory cells are very similar 



* Zool. Jahrb., xxxv. (1913) pp. 533-80 (2 pis.;. 



t Arkiv Zool., viii. (1913) No. 4, pp. 1-19 (2 pis. and 10 figs.). 



j Arch. Zool. Exp6r., liii. (1913) pp. 139-274 (4 pis.). 



